1. Field of the Invention
The invention relates to a safety hypodermic syringe, especially to a syringe in which a plunger thereof is recyclable, a needle hub thereof is able to be securely installed, a needle thereof need notstick out from a barrel thereof after use, medical liquid contained therein after use is less than conventional syringes, and whether it has been used is able to be clearly indicated by a security bar.
2. Description of Related Art
A hypodermic syringe is a common medical instrument which is used in a large amount every day. Present hypodermic syringes are one-time use type and can be discarded after use. To prevent needles of such used syringes hurting people, safety syringes whose needles can be pulled back into barrels thereof have been provided. One typical type of such safety syringes is as shown in FIG. 9. In the figure, it is seen that the syringe has a barrel (62), a plunger (63) contained in the barrel (62), and a needle hub (60) installed on an upper end (61) of a needle seat contained in a top tube of the barrel (62). A stopper is formed on a top of the plunger (63) and hermetically contacts with an inner surface of the barrel (63). A central pole with an enlarged head is formed on the stopper. At the end of an injection process, the head enters a rear cavity of the seat and engages with a pair of small protrusions (600). Then, by pulling back the plunger (63), the head will drive the seat, and thus the needle installed on the seat, backward into the barrel (62). To indicate whether the syringe has been used, a security cord (64) is provided being formed on a finger flange of the syringe and extending downward to engage with a thumb rest (65) of the syringe. The security cord (64) is so thin that once the plunger (63) is pulled back with respect to the barrel (62) to suck medical liquid into the syringe, it will break to indicate that the syringe has been used.
However, this kind of conventional safety syringe has some drawbacks:
1. in actual use, it is found there is always some medical liquid remaining in the rear cavity thereof and this will cause unnecessary waste;
2. the needle hub (60) stays on the seat just by a certain friction force therebetween and therefore it may fall off from the seat;
3. after use, the plunger (63) cannot be removed from the syringe and this means the plunger (63) is not recyclable;
4. after use and the needle having been pulled back into the barrel (62), there is still the possibility that the plunger (63) is pushed by accident to drive the needle out of the barrel (62) again, which is obviously dangerous; and,
5. the security cord is too thin and may break by accident before the syringe is really used, which may also cause waste.
The main object of the invention is to provide a safety hypodermic syringe wherein a plunger thereof is recyclable, a needle hub thereof is able to be securely installed, a needle thereof will not stick out from a barrel thereof after use, medical liquid contained therein after use is less than conventional syringes, and whether it has been used is able to be plainly indicated by a security bar.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.